A generator and power transmission system of wind energy converters have a strong influence on the economic efficiency of generating energy from wind. A wind energy converter generally has a wind turbine with a transmission that includes a mechanical gear unit in order to use conventional generators within their normal range of operation. High fluctuations in rotor torque that may be caused by gusts of wind are a major problem in wind energy generating systems. Such rotor torque fluctuations can lead to the use of gear boxes in the transmissions that may be twice the weight of the generator itself. Such gear boxes may greatly increase the cost of a wind energy converter.
In addition, mechanical transmissions generally decrease the converter efficiency, making wind turbines with a convention mechanical transmission unfavorable with respect to mass and efficiency. Other disadvantages, such as wear, maintenance and noise emissions should be considered when designing and building a wind turbine.